Initial selectivity of herbicides applied in post-emergence of showy crotalaria

Abstract

Among the practices that aim to confer sustainability of the agricultural soil, the use of green manure and/or cover crops such as crotalaria are advocated. The management of weeds is one of the practices for the success of crotalaria. However, the information about the selectivity of herbicide are scarce and these are of paramount importance. The objective of this study was to evaluate the selectivity of different herbicides applied in post-emergence of showy crotalaria (Crotalaria spectabilis). Two experiments were conducted in a greenhouse in a randomized completely randomized design with four replications. In the first one the following herbicides were tested. The first experiment involved the following herbicides (g. i.a.ha^-1): atrazine (500 and 1000), bentazon (720), carfentrazone-ethyl (3.75), clomazone (400), diclosulam (20), diuron (800), ethoxysulfuron (18), flumioxazin (10), mesotrione (60), oxadiazon (500), tembotrione (40), atrazine + flumioxazin + carfentrazone-ethyl (300 + 5 + 2), and a control without application. In the second were used, bentazon (400), clomazone (400), diclosulam (10 and 15), diuron (400), ethoxysulfuron (15), bentazon + diclosulam (200 + 7.5), diclosulam + diuron (7.5 + 200), bentazon + diuron (200 + 200) and a control without application. Phytotoxicity was evaluated at 7, 14, 21 and 28 days after application (DAA) and aerial dry matter (ADM) at 28 DAA. In both experiments the herbicides bentazon, clomazone, diclosulam and ethoxysulfuron caused low injuries to the crop and low reduction in ADM. The herbicides atrazine, mesotrione, oxadiazon and atrazine + flumioxazin + carfentrazone-ethyl provided high levels of injuries and high reduction in ADM. The herbicides bentazon, clomazone, diclosulam and ethoxysulfuron were selectivity for post-emergence application of the crop.